In Fable 3, can I have several wives in the same city?

Nothing's stopping you from marrying multiple people, but you can only have one "proper" relationship. That is to say, Fable 3 does not recognize polyamorism.

The exceptions to this are:

• Other cities. You can have one "actual" relationship per city.
• Other players. NPCs do not recognize a marriage to another player.

The only restriction is you can only have one spouse per property you own in a city. That said, if you have more than one marriage in the same city, all spouses you have in that city will be quickly looking for a divorce.